Implement Short/Small String Optimization in SBUF(9) and change lengths and

positions in the API from ssize_t and int to size_t.

CR:		D388
Approved by:	des, bapt

3 files changed, 23 insertions, 11 deletions

diff --git a/lib/libsbuf/Makefile b/lib/libsbuf/Makefile
index 79d3fe973e05..42d4a4e4674c 100644
--- a/lib/libsbuf/Makefile
+++ b/lib/libsbuf/Makefile
@@ -4,7 +4,7 @@ LIB=		sbuf
 SHLIBDIR?= 	/lib
 SRCS=		subr_sbuf.c 
 
-SHLIB_MAJOR	= 6
+SHLIB_MAJOR	= 7
 
 SYMBOL_MAPS=    ${.CURDIR}/Symbol.map
 VERSION_DEF=	${.CURDIR}/Version.def
diff --git a/sys/kern/subr_sbuf.c b/sys/kern/subr_sbuf.c
index 1490bc6ebd44..a0f3b7e71f9d 100644
--- a/sys/kern/subr_sbuf.c
+++ b/sys/kern/subr_sbuf.c
@@ -152,11 +152,16 @@ static int
 sbuf_extend(struct sbuf *s, int addlen)
 {
 	char *newbuf;
-	int newsize;
+	size_t newsize;
 
 	if (!SBUF_CANEXTEND(s))
 		return (-1);
 	newsize = sbuf_extendsize(s->s_size + addlen);
+	if (s->s_buf == s->s_static_buf && newsize <= sizeof(s->s_static_buf)) {
+		s->s_size = sizeof(s->s_static_buf);
+		return (0);
+	}
+
 	newbuf = SBMALLOC(newsize);
 	if (newbuf == NULL)
 		return (-1);
@@ -176,7 +181,7 @@ sbuf_extend(struct sbuf *s, int addlen)
  * big enough to hold at least length characters.
  */
 static struct sbuf *
-sbuf_newbuf(struct sbuf *s, char *buf, int length, int flags)
+sbuf_newbuf(struct sbuf *s, char *buf, size_t length, int flags)
 {
 
 	memset(s, 0, sizeof(*s));
@@ -195,6 +200,11 @@ sbuf_newbuf(struct sbuf *s, char *buf, int length, int flags)
 	if ((flags & SBUF_AUTOEXTEND) != 0)
 		s->s_size = sbuf_extendsize(s->s_size);
 
+	if (s->s_size <= sizeof(s->s_static_buf)) {
+		s->s_buf = s->s_static_buf;
+		return (s);
+	}
+
 	s->s_buf = SBMALLOC(s->s_size);
 	if (s->s_buf == NULL)
 		return (NULL);
@@ -283,21 +293,19 @@ sbuf_clear(struct sbuf *s)
  * Effectively truncates the sbuf at the new position.
  */
 int
-sbuf_setpos(struct sbuf *s, ssize_t pos)
+sbuf_setpos(struct sbuf *s, size_t pos)
 {
 
 	assert_sbuf_integrity(s);
 	assert_sbuf_state(s, 0);
 
-	KASSERT(pos >= 0,
-	    ("attempt to seek to a negative position (%jd)", (intmax_t)pos));
 	KASSERT(pos < s->s_size,
 	    ("attempt to seek past end of sbuf (%jd >= %jd)",
 	    (intmax_t)pos, (intmax_t)s->s_size));
 	KASSERT(!SBUF_ISSECTION(s),
 	    ("attempt to seek when in a section"));
 
-	if (pos < 0 || pos > s->s_len)
+	if (pos > s->s_len)
 		return (-1);
 	s->s_len = pos;
 	return (0);
@@ -561,7 +569,8 @@ int
 sbuf_vprintf(struct sbuf *s, const char *fmt, va_list ap)
 {
 	va_list ap_copy;
-	int error, len;
+	size_t len;
+	int error;
 
 	assert_sbuf_integrity(s);
 	assert_sbuf_state(s, 0);
diff --git a/sys/sys/sbuf.h b/sys/sys/sbuf.h
index 9816a4cd6c54..9c794c830543 100644
--- a/sys/sys/sbuf.h
+++ b/sys/sys/sbuf.h
@@ -44,8 +44,8 @@ struct sbuf {
 	sbuf_drain_func	*s_drain_func;	/* drain function */
 	void		*s_drain_arg;	/* user-supplied drain argument */
 	int		 s_error;	/* current error code */
-	ssize_t		 s_size;	/* size of storage buffer */
-	ssize_t		 s_len;		/* current length of string */
+	size_t		 s_size;	/* size of storage buffer */
+	size_t		 s_len;		/* current length of string */
 #define	SBUF_FIXEDLEN	0x00000000	/* fixed length buffer (default) */
 #define	SBUF_AUTOEXTEND	0x00000001	/* automatically extend buffer */
 #define	SBUF_USRFLAGMSK	0x0000ffff	/* mask of flags the user may specify */
@@ -55,6 +55,9 @@ struct sbuf {
 #define	SBUF_INSECTION	0x00100000	/* set by sbuf_start_section() */
 	int		 s_flags;	/* flags */
 	ssize_t		 s_sect_len;	/* current length of section */
+#define SBUF_STATIC_LEN	64		/* static storage buffer length */
+	char		 s_static_buf[SBUF_STATIC_LEN];
+					/* static storage buffer */
 };
 
 __BEGIN_DECLS
@@ -65,7 +68,7 @@ struct sbuf	*sbuf_new(struct sbuf *, char *, int, int);
 #define		 sbuf_new_auto()				\
 	sbuf_new(NULL, NULL, 0, SBUF_AUTOEXTEND)
 void		 sbuf_clear(struct sbuf *);
-int		 sbuf_setpos(struct sbuf *, ssize_t);
+int		 sbuf_setpos(struct sbuf *, size_t);
 int		 sbuf_bcat(struct sbuf *, const void *, size_t);
 int		 sbuf_bcpy(struct sbuf *, const void *, size_t);
 int		 sbuf_cat(struct sbuf *, const char *);